Submillimeter H 2 O and H 2 O + emission in lensed ultra- and hyper-luminous infrared galaxies at z ~ 2-4
Journal article, 2016
We report rest-frame submillimeter H2O emission line observations of 11 ultra- or hyper-luminous infrared galaxies (ULIRGs or HyLIRGs) at z ∼ 2-4 selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Using the IRAM NOrthern Extended Millimeter Array (NOEMA), we have detected 14 new H2O emission lines. These include five 321-312 ortho-H2O lines (Eup/k = 305 K) and nine J = 2 para-H2O lines, either 202-111 (Eup/k = 101 K) or 211-202 (Eup/k = 137 K). The apparent luminosities of the H2O emission lines are μLH2O ∼ 6-21 × 108 L⊙ (3 > μ > 15, where μ is the lens magnification factor), with velocity-integrated line fluxes ranging from 4-15 Jy km s-1. We have also observed CO emission lines using EMIR on the IRAM 30 m telescope in seven sources (most of those have not yet had their CO emission lines observed). The velocity widths for CO and H2O lines are found to be similar, generally within 1σ errors in the same source. With almost comparable integrated flux densities to those of the high-J CO line (ratios range from 0.4 to 1.1), H2O is found to be among the strongest molecular emitters in high-redshift Hy/ULIRGs. We also confirm our previously found correlation between luminosity of H2O(LH2O) and infrared (LIR) that LH2O ∼ LIR1:1-1:2, with our new detections. This correlation could be explained by a dominant role of far-infrared pumping in the H2O excitation. Modelling reveals that the far-infrared radiation fields have warm dust temperature Twarm ∼ 45-75 K, H2O column density per unit velocity interval NH2O/ΔV ≳ 0:3 × 1015 cm-2 km-1 s and 100 μm continuum opacity τ100 1 (optically thick), indicating that H2O is likely to trace highly obscured warm dense gas. However, further observations of J ≥ 4 H2O lines are needed to better constrain the continuum optical depth and other physical conditions of the molecular gas and dust. We have also detected H2O+ emission in three sources. A tight correlation between LH2O and LH2O+ has been found in galaxies from low to high redshift. The velocity-integrated flux density ratio between H2O+ and H2O suggests that cosmic rays generated by strong star formation are possibly driving the H2O+ formation. © 2016 ESO.
Radio lines: ISM
ISM: molecules
Galaxies: ISM
Submillimeter: galaxies
Infrared: galaxies
Galaxies: high-redshift
Author
C. Yang
University of Paris-Sud
Pierre and Marie Curie University (UPMC)
Chinese Academy of Sciences
Centre national de la recherche scientifique (CNRS)
A.A. Omont
Centre national de la recherche scientifique (CNRS)
Pierre and Marie Curie University (UPMC)
A. Beelen
University of Paris-Sud
E. Gonzalez-Alfonso
University of Alcalá
R. Neri
Institut de Radioastronomie Millimétrique (IRAM)
Y. Gao
Chinese Academy of Sciences
P. van der Werf
Leiden University
A. Weiß
Max Planck Society
R. Gavazzi
Pierre and Marie Curie University (UPMC)
Centre national de la recherche scientifique (CNRS)
Niklas Falstad
Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics
A. J. Baker
Rutgers University
R. S. Bussmann
Cornell University
A. Cooray
University of California at Irvine (UCI)
P. Cox
Atacama Large Millimeter-submillimeter Array (ALMA)
H. Dannerbauer
University of Vienna
S. Dye
University of Nottingham
M. Guélin
Institut de Radioastronomie Millimétrique (IRAM)
R. J. Ivison
European Southern Observatory (ESO)
University of Edinburgh
M. Krips
Institut de Radioastronomie Millimétrique (IRAM)
M. Lehnert
Pierre and Marie Curie University (UPMC)
Centre national de la recherche scientifique (CNRS)
M. J. Michalowski
University of Edinburgh
D. A. Riechers
Cornell University
M. Spaans
University of Groningen
E. Valiante
Cardiff University
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 595 Art no A80- A80Subject Categories
Astronomy, Astrophysics and Cosmology
Roots
Basic sciences
Infrastructure
Onsala Space Observatory
DOI
10.1051/0004-6361/201628160